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Anatomical drivers of stomatal conductance in sorghum lines with different leaf widths grown under different temperatures
No full textSustaining crop productivity and resilience in water-limited environments and under rising temperatures are matters of concern worldwide. We investigated the leaf anatomical traits that underpin our recently identified link between leaf width (LW) and intrinsic water use efficiency (iWUE), as traits of interest in plant breeding. Ten sorghum lines with varying LW were grown under three temperatures to expand the range of variation of both LW and gas exchange rates. Leaf gas exchange, surface morphology and cross-sectional anatomy were measured and analysed using structural equations modelling. Narrower leaves had lower stomatal conductance (gs) and higher iWUE across growth temperatures. They also had smaller intercellular airspaces, stomatal size, percentage of open stomatal aperture relative to maximum, hydraulic pathway, mesophyll thickness, and leaf mass per area. Structural modelling revealed a developmental association among leaf anatomical traits that underpinned gs variation in sorghum. Growing temperature and LW both impacted leaf gas exchange rates, but only LW directly impacted leaf anatomy. Wider leaves may be more productive under well-watered conditions, but consume more water for growth and development, which is detrimental under water stress
Combining nitrification inhibitors with a reduced N rate maintains yield and reduces N2O emissions in sweet corn
No full textIntensive vegetable production is characterised by high nitrogen (N) application rates and frequent irrigations, promoting elevated nitrous oxide (N2O) emissions, a powerful greenhouse gas indicative for the low N use efficiency (NUE) in these systems. The use of nitrification inhibitors (NI) has been promoted as an effective strategy to increase NUE and decrease N2O emissions in N-intensive agricultural systems. This study investigated the effect of two NIs, 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (Piadin), on N2O emissions and 15N fertiliser recovery in a field experiment in sweet corn. The trial compared the conventional fertiliser N rate to a 20% reduced rate combined with either DMPP or Piadin. The use of NI-coated urea at a 20% reduced application rate decreased cumulative N2O emissions by 51% without yield penalty. More than 25% of applied N was lost from the conventional treatment, while a reduced N rate in combination with the use of a NI significantly decreased N fertiliser losses (by up to 98%). Across treatments, between 30 and 50% of applied N fertiliser remained in the soil, highlighting the need to account for residual N to optimise fertilisation in the following crop. The reduction of overall N losses without yield penalties suggests that the extra cost of using NIs can be compensated by reduced fertiliser application rates, making the use of NIs an economically viable management strategy for growers while minimising environmentally harmful N losses from vegetable growing systems
Conditioning to predators improves survival of stocked Murray cod (Maccullochella peelii) fingerlings
Get PDFContext: Following recent major fish kill events, there is increasing interest in stocking Murray cod fingerlings to help fish stocks recover. Strategies that can increase post-release survival of stocked fingerlings are important for conservation stocking of Murray cod and may also have application to other species.Aims: The aim of this work was to evaluate whether pre-release predator recognition and avoidance training conferred a survival advantage on stocked Murray cod (Maccullochella peelii) fingerlings. Predator-free release enclosures were also evaluated as a method to improve survival.Methods: Fingerlings were trained by exposure to predators and skin extract. Fingerlings were marked with visual implant elastomer (VIE) tags to denote training status and release strategy (trained, untrained, soft release, standard release). Fingerlings were released at three sites in the northern Murray–Darling Basin. Marked fish were recaptured by electrofishing 24 h post-release and quarterly up to 15 months post-release.Key results: Trained Murray cod had higher relative survival than did untrained fish. The mean recapture rate of trained fish was twice that of untrained fish. Fingerlings released directly into the waterbody had significantly higher recapture rates than did fingerlings acclimated for 90 min in predator-free enclosures.Conclusions: Predator conditioning training provides a survival advantage to stocked Murray cod fingerlings. However, predator-free release enclosures conferred a disadvantage.Implications: Pre-release training of Murray cod fingerlings could be beneficial to conservation and recreational-fish stocking programs. We recommend stocking trained cod fingerlings directly into the receiving environment, rather than into soft-release enclosures, so as to maximise their chance of survival
Molecular Cues for Phenological Events in the Flowering Cycle in Avocado
Get PDFReproductively mature horticultural trees undergo an annual flowering cycle that repeats each year of their reproductive life. This annual flowering cycle is critical for horticultural tree productivity. However, the molecular events underlying the regulation of flowering in tropical tree crops such as avocado are not fully understood or documented. In this study, we investigated the potential molecular cues regulating the yearly flowering cycle in avocado for two consecutive crop cycles. Homologues of flowering-related genes were identified and assessed for their expression profiles in various tissues throughout the year. Avocado homologues of known floral genes FT, AP1, LFY, FUL, SPL9, CO and SEP2/AGL4 were upregulated at the typical time of floral induction for avocado trees growing in Queensland, Australia. We suggest these are potential candidate markers for floral initiation in these crops. In addition, DAM and DRM1, which are associated with endodormancy, were downregulated at the time of floral bud break. In this study, a positive correlation between CO activation and FT in avocado leaves to regulate flowering was not seen. Furthermore, the SOC1-SPL4 model described in annual plants appears to be conserved in avocado. Lastly, no correlation of juvenility-related miRNAs miR156, miR172 with any phenological event was observed
Photodynamic Inactivation of Botrytis cinerea Spores by Curcumin—Effect of Treatment Factors and Characterization of Photo-generated Reactive Oxygen Species
Get PDFBotrytiscinerea is the main cause of gray mold in a wide range of fresh produce, which causes huge losses in pre- and/or post-harvest stages and is therefore considered the second major plant pathogen globally. Since the application of synthetic fungicides is not allowed in postharvest conditions, alternative natural approaches are required to reduce the resulting spoilage. The aim of this study was to investigate the efficacy of photodynamic treatment in inactivating B. cinerea spores in vitro, for which the interactive effect of influential treatment parameters on curcumin phototoxicity was studied using an I-optimal design. Results showed that the antifungal activity of the treatment was significantly dependent on solvent, curcumin concentration, and irradiance, except for light dose. A complete photoinactivation of spores was obtained in an aqueous ethanolic environment (optimum condition: 13 μM, 31.75 mW cm−2, 19.05 J cm−2), compared to when curcumin was dissolved in medium-chain-triglyceride (MCT) oil. Furthermore, the photogeneration of superoxide anion and hydroxyl radicals was demonstrated by electron paramagnetic resonance spectroscopy, which indicates the occurrence of a type-I photodynamic reaction. These findings suggest that curcumin-based photosensitization can inhibit/reduce fungal infection, which can be employed in pre/post-harvest stages to reduce the waste caused by spoilage
Australian cattle herd: a new perspective on structure, performance and production
Get PDFContext: Businesses within the Australian cattle industries and associated research and advisory agencies require accurate data on production and performance of the national herd. Currently, these are derived from survey and statistical data; the latter is expected to be accurate, but the former needs to be tested in view of information suggesting significant under-reporting.Aims: The research aimed to define the structure, performance and liveweight production of the Australian cattle herd and describe changes in reproduction, growth and survival over the past 40–50 years.Methods: Interactive static herd modelling of beef and dairy herds was reconciled each year from 1976 to 2018, using slaughter and live export statistics and surveyed dairy cow numbers. A principle applied was that model performance should dictate input variables, moderating information derived from publications and professional opinion.Key results: The Australian cattle herd fluctuated in size till the mid-1980s from when it settled into a range of 30–40 million beef cattle (12–16 Mt), exceeding survey data by 56–75%. The dairy herd remained at ~10% of the beef herd. Despite consistent herd size, productivity of the cattle herd increased from ~2.5 to 4.5 Mt of liveweight annually over 35 years. Half of this change was due to reductions in mortality, though ~1 million post-weaning-age cattle still die annually, in addition to >0.5 million calves from birth to weaning. Approximately a quarter each of the change was due to increased reproductive output and to steer growth. Liveweight production per beef animal increased from 70–75 kg/year to 130–135 kg/year, while liveweight production ratio increased by 0.08 and 0.12 kg/kg of cattle in male and female beef cattle respectively, to reach 0.31 kg/kg of cattle.Conclusions: The main conclusion is the size, performance, production and productivity of the Australian cattle herd are quite different from that determined from surveys. Also, there is an on-going opportunity to derive benefit from improving cattle survival, reproduction and growth and from improving the feed base.Implications: This research may have large impact on priorities for Australian beef business and associated environmental management. It is recommended that surveys be used to derive relative values to use in combination with absolute statistical data to derive accurate herd measures
Taxonomic Delineation of the Old World Species Stomphastis thraustica (Lepidoptera: Gracillariidae) Feeding on Jatropha gossypiifolia (Euphorbiaceae) that Was Collected in the New World and Imported as a Biocontrol Agent to Australia
No full textWe provide the identification and species delineation of this biocontrol agent as Stomphastis thraustica (Meyrick in Trans Ent Soc Lond 80(1):107–120, 1908) belonging to the family Gracillariidae. We clarify the distribution pattern of S. thraustica, its host plant preferences, and present taxonomic and molecular diagnoses based on original morphological and genetic data as well as data retrieved from historic literature and genetic databases. Following our own collecting efforts in three continents Africa, South America, and Australia as well as our study of historic museum collection material, we present many new distribution records of S. thraustica for countries and territories in the world including the new discovery of this species in the Neotropical region and we report its introduction in Australia as a biocontrol agent. Using mitogenomic and COI gene data, we clarified that the closest relative of S. thraustica is Stomphastis sp. that occurs in Madagascar and Australia and feeds on the same host plant as S. thraustica – Jatropha gossypiifolia L. (Euphorbiaceae). The molecular sequence divergence in the mitochondrial DNA barcode fragment between these two closely related species S. thraustica and Stomphastis sp. is over 5.7% supporting that they are different species
Swimming against the stream: A systems approach to rebuilding fishing stocks
No full textSolutions occurring within complex systems such as recovery of species are urgently needed. One path forward involves action agendas that extend across the full range of stakeholder groups. Approaches that can foster cooperative behavior across a range of vested interests can create environments supporting species recovery. This paper reports the stakeholder identification process used to gather divergent opinions. A total of 923 priorities from 239 stakeholders were identified. Consensus approaches were utilized, resulting in 25 top priorities, selected by 61 stakeholders. This study demonstrates how consensus areas for action can be illuminated and supported by diverse stakeholder groups whose relationships have previously been indicated as antagonistic. Results indicate support for a range of actions that can be implemented to protect iconic fish species such as pearl perch and snapper in Southeast Queensland. Stakeholders supported actions that; change fishing practices for groups (recreational, commercial and charter); extended monitoring and reporting; improved compliance; changes to fishing management practices; extended fishing control measures and the construction of additional artificial reef habitats
Flight activity and dispersal of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) across a mixed agricultural landscape in southern Australia
No full textTo better understand the field ecology of stored grain beetles in southern Australia we monitored the flight activity of Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst) over a 2 year period. We used target-specific pheromone lures and Lindgren funnel traps in open fields, at grain storages, and in remnant native vegetation. Over 35,000 R. dominica and 2,500 T. castaneum were caught. Significantly more R. dominica (46.4%) were caught in areas of remnant vegetation than at storage sites (29.2%) or in open fields (24.4%), suggesting this species may be utilising non-grain food sources in some areas. In contrast, the majority of T. castaneum (45.4%) were caught adjacent to storages. An intense summer heatwave (14 day mean maximum air temperature 41.9 °C) corresponded to captures of both species declining to near zero until the following spring. Sex ratios of both species varied significantly over time but were unaffected by habitat type. Two mark/release/recapture (MRR) trials using laboratory-reared R. dominica were conducted using a 1 km trap array and pheromone lures. The recovery rate for marked beetles in the first trial was 1.41%, however a subsequent experiment comparing fresh and weathered lures showed that lure attractancy declines to 50% between 3 and 4 days after deployment during hot weather (mean daily maximum air temperature 29.4 °C). When the MRR trial was repeated with lures replaced at shorter (2 day) intervals, the recovery rate rose to 3.27% and the number of wild R. dominica captured increased proportionately. The short half-life of rubber septum-based R. dominica pheromone lures needs to be considered when designing surveillance programs, particularly if attempts are being made to correlate R. dominica dispersal patterns to short-term weather events
Spanner Crab Fishery Level 1 Ecological Risk Assessment
Get PDFThe Queensland Ecological Risk Assessment Guideline (the Guideline) was released in March 2018 as part of the Queensland Sustainable Fisheries Strategy 2017–2027. This Guideline provides an overview of strategy being employed to develop Ecological Risk Assessments (ERAs) for Queensland’s fisheries. The Guideline describes a four-stage framework consisting of a Scoping Study; a Level 1, whole of fishery qualitative assessment; a Level 2, species-specific semi-quantitative or low-data quantitative assessment and; a Level 3 quantitative assessment (if applicable).
The aim of the Level 1 ERA is to produce a broad risk profile for each fishery based on a qualitative ERA method described by Astles et al. (2006). The method considers a range of factors including the current fishing environment (e.g. current catch, effort and licensing trends), limitations of the current management arrangements (e.g. transfer of effort to already saturated markets, substantial increases in fishing mortality for key species, changing target species) and life-history constraints of the species being assessed. In the Spanner Crab Fishery the Level 1 ERA assessed fishing related risks in 15 ecological components including target species, bycatch, marine turtles, sea snakes, crocodiles, dugongs, cetaceans (whales and dolphins), protected teleosts, batoids, sharks, syngnathids, seabirds, terrestrial mammals, marine habitats and ecosystem processes.
The Level 1 ERA indicates that the Spanner Crab Fishery presents a low to negligible risk to most of ecological components. At low/intermediate, target species had the highest risk rating of the assessment. These risks are being managed effectively through a range of measures including a fishery-specific harvest strategy